Loading a file... but there is a small error

The comments are in danish so you probably wont understand them, but since the code is fairly simple I don't think it will be a problem.

The error is this:
If you are to load a file that contains nothing but a sign (like 'g') and exactly "one" new line (that is '/n' - though it with dos is "/r/n") then there will be added one more sign to the loaded text -WHY!

Code:

AnsiString TTextFile::Load() const
{
  AnsiString Buffer;
  int Length;

  ifstream File(itsPath.c_str());

  if (File.is_open())
  {
    File.seekg(0, ios::end);

    Length = File.tellg();

    Buffer.SetLength(Length + 1);

    File.clear(); /* File nulstilles så funktioner som eof(), fail(), good() og bad() retunere det som de altid gør når en
                     ny stream bliver lavet. */
    File.seekg(0, ios::beg); /* File's itterator (pointeren der peger på det tegn der ved næste kald skal læses eller overskrives)
                                //bliver sat tilbage til starten af filen */

    File.read(Buffer.c_str(), Length);
    Buffer[Length + 1] = '\0';

    File.close();
  }

  return Buffer;
}

If the length of the buffer is Length+1, then Length+1 is an invalid index.
If you read Length bytes, then the buffer will be filled from [0] to [Length-1]. So you want to put the null terminator at [Length].

gg

Yeah you might think so, but this code is made with borlands AnsiString instead of string, and when you use AnsiString it starts with 1 instead of zero. - Besides... I've checked.

Code:

std::string str;
getline(File,str,EOF);
AnsiString Buffer(str.c_str());

potental problems:
1. If file is opened for text this will stop at an embeded EOF char for your environments conventions (likely ^Z or ^D)
2. This will stop at an embeded (char)-1
3. AnsiString's constructor must take a char* and will stop on an embeded '\0' (though std::string has no problem here)

I've tested the following three while loops and it is only the one Salem have shown me that actually works without reading to few or to many characters.
Why is that?
Besides... I thought get() returned istream& and not something that could prove to be usefull in a if/while etc. statement.

Code:

    while (File.get(ch))
    {
      File.get(ch);
      Buffer[i++] = ch;
    }

    while (i <= Length && File.good())
    {
      File.get(ch);
      Buffer[i++] = ch;
    }*/

    while (i <= Length && File.get(ch))
    {
      Buffer[i++] = ch;
    }

Furthermore I find it a bit funny that write() worked out allright but not read().

Code:

  if (File.is_open())
  {
    File.write(str.c_str(), str.Length());

    File.close();
  }

This FAQ describes the problem you have observed, except it demostrates the issue in C, not C++.

gg

> I thought get() returned istream& and not something that could prove to be usefull in a if/while etc. statement

The istream that is returned by get() is evaluated by the if/while statement which will call the "operator void *()" method of the istream. This overloaded operator returns: "fail() ? 0 : (void*)this)" - which makes it very usefull in if/while statements.

gg

As a last question (on this thread ) why the i <= length? Wouldn't File.get(ch) not always end the loop when needed?